The cell free translation of RNA isolated from murine leukemia virus (MLV) and MLV specific mRNA will be attempted in a purified system utilizing ribosome subunits, initiation factors, S100 and other necessary ingredients. Reverse transcription of MLV RNA, performed in vitro, results in the synthesis of DNA molecules only about 100 nucleotides long, presumably due to the presence of extensive secondary structure in the RNA. It is anticipated that this secondary structure may hinder faithful translation. If this should be the case, the use of T4 gene 32 protein will be explored in an endeavor to solve this problem and also the associated one of in vitro RNA yields DNA transcription. The cell free translation system will be used to study RNA isolated from both wild and mutant virus in an endeavor to correlate the genes with their products. Detailed analysis of polypeptides synthesized in vitro will be performed by a combination of immunoadsorption, electrophoresis in SDS-polyacrylamide gel and tryptic fingerprinting. This study should provide a procedure of translating all the genes of MLV and the in vitro synthesis of DNA corresponding to 35S RNA for use in later studies using specific restriction enzymes for detailed mapping of the genome. Protocols are being developed to determine a detailed physical map of the DNA reverse transcript utilizing a battery of restriction endonuclease enzymes. Cell free systems have provided a major tool for the detailed biochemical study of bacteriophage lambda and bacterial operons. The expansion of the use of such system to the study of RNA tumor viruses should provide a powerful tool for the thorough biochemical analysis of RNA tumor virus and their role in neoplasia.